theschoens

1990 LS 400 now at 250K has slow power steering leak. Dealer says replace power steering pump and valve, but couldn't pinpoint source of leak. Had power steering pump rebuilt at 166K, rebuilt alternator at 168K. Got new power steering rack at 235K. Got new high pressure pwr steering hose at 238K. Thats the history, car is new to us. Power steering still leaking, must add fluid every 2 weeks or so. Any easy ways to troubleshoot if leak is in return lines, or identify source of leak. Why would I need a new power steering pump if this one works fine with fluid? Can a mechanic easily remove idle air control valve? Am thinking this baby has been leaking for a while (but alternator is still working!) and previous owner kept changing out parts trying to stop leak. Any ideas on what you would do? Am not mechanically inclined-will have to have mech do it. Thanks

CUMan

The most logical thing to check would be the air control valve. If this valve is leaking, there are no visible signs of fluid because it is being drawn into the engine and burned. A good clue for this being the problem is a white puff of smoke from the exhaust when you crank the car. However, if the volume of fluid being leaked is small, this would not necessarily occur.

Yes, your mechanic can easily remove the air control valve. It screws into the bottom of the power steering pump.

You can check for leakage in this valve by detaching the two hoses that run from the valve at the nipples where they attach to the air intake and manifold. Seal off the ends of the hoses by putting a screw or something similar into them. You would also need to seal off the two points where they attach to the air intake and engine. You will not do any harm by trying this for a few days. You might not even notice a difference in the car's operation.

If the power steering fluid loss stops while you have these hoses disconnected, you have found your problem. The part number for the valve is 17630-16040. It should cost about $70.00 and should be available at any Lexus or Toyota dealer.

This is a very common problem on first and second generation LS models and has been discussed numerous times. Do a "Search" for more discussion.

theschoens

Thanks CUMan, have the telltail white smoke on start-up so I ordered the valve. Is it easily accessible if I can put it on a lift, or does a mech need to do it? Thought I might give it a shot if there's not too much to it. Looked at the threads I could find, but didn't really see a "how to". One of them talked about taking the alternator off first--that's when I thought mech. Any suggestions are welcome.

CUMan

I would suggest that you let a mechanic do this job.

I do a lot of my own maintenance (oil changes, brakes, etc.), but I didn't attempt this myself. I assumed that tools would be needed which I didn't have.

A well-equipped shop should be able to do it in less than an hour.

By the way, I would suggest that you also have them replace the two hoses that connect the valve to the air intake and intake manifold. Those hoses were very hardened on my 93 LS and were cracked. Yours probably have not been replaced and are probably hard and brittle.

theschoens

Thanks, I'll change the hoses out too. Appreciate your advice on the valve. Was about to just replace the whole power steering pump AGAIN (would have still had the leak and been scratching my head )

damon

When you buy a PS pump, even a brand new one from Lexus, it arrives with a plug installed where the Idle Air Control Valve screws in. Or if you prefer, it is in the configuration a SC model would use since it is the same pump wo the valve. The valve has no effect on PS pump lifespan or operation.

PS Pump hydraulic pressures are indeed very high, the pressure in the vacuum lines however is not very high & a totally seperate issue. All you are after here is to preserve normal maf function & have no vacuum leaks at the manifold. 2 plugs would do the same thing as "looping" that you have read about.

Hints: Never change a PS Pump wo doing the Pressure hose as well. Use a high quality PS Fluid and change it every 30,000 miles. I'm switching to Royal Purple when I get a chance.

B.Diddy

iTrader: (1)

I have a PS system leak as well. I was reading that the Idle Air valve on the pump could be the culprit. My question is this: Can we swap to an SC400 valveless PS pump? and just bypass the valve altogether?

Anyone have more details?

damon

B. Diddy,

Perhaps I'm not being clear. It is the same damn pump!! An SC does not have an IAC valve & you don't have to either. If you drove my 94 LS & I did not inform you of this you would not know the difference.

CUMan

I doubt you would notice the difference if you installed the SC pump without the air control valve.

Before I had the air control valve replaced in my 93 LS, I had the valve sealed off for about two weeks because it was leaking so much fluid into the intake manifold. The only difference I noticed was a slight decrease in the idle speed.

B.Diddy

iTrader: (1)

So bottom line.... what is the problem in this common case? seals in the PS pump? or the Hoses giving up after a decade?

How about some good help cause its 25* outside and dont really wanna go jack up the car right this minute.

I'd like to gather some info so I can better diagnose this issue when I peek under there when the weather breaks.

CUMan

B.Diddy -

I don't really follow what you are asking. Are you asking how the air control valve fails? Are you asking why the power steering system leaks?

There are several parts of the LS power steering that can cause leaks. Probably the most common - and the cheapest and easiest to fix - involves the air control valve. The failure is the valve itself. It apparently fails because the seals or o-rings inside the valve break down and allow fluid to enter hoses which are supposed to be air hoses. This fluid is drawn into the engine and is burned, causing the white smoke at start-up.

The hoses involved with the air control valve would probably not fail very often; but, as with any rubber hoses, they get hard and brittle as they age. When you attempt to pull these old hoses off their connections at the air control valve, they will likely be difficult to remove and will crack. This could easily lead to vacuum leaks. This is why I suggested in the earlier post that they be replaced when the valve is replaced. No special OEM parts are needed to replace these hoses. Just use the correct size rubber hose that you can get from any auto parts store.

If you are losing PS fluid, and you suspect that the air control valve is the problem, do as I suggested in the earlier post. Seal off the valve and see if the fluid loss stops. If it does, consider yourself lucky. You can fix the leak with a part that costs about $80.00.

Lexushead

I've had PS fluid leaking for the last 30,000 miles now (3yrs). A slow leak. I just keep adding the fluid and the STOP LEAK fluid. STOP LEAK seems to help slow done the leak. I don't know where the leak is because it's too damn hard to find. If the PS fail, I guess I'll be getting some workout.

tedvitale

I took my '92 LS 400 (manufactured 8/91) in to my mechanic because it's been leaking spots on my driveway and he said the leak appears to be from the passenger side of the rack. The boot is torn also. I was going to have it replaced until I heard the price on the part. I set out to get some prices myself but there are EVO and non EVO racks. I called the supplier at A1Cardone and they can't tell me what the EVO is. I called Lexus and they can't tell me what the hell it is either. Anybody know what the difference is between an EVO and non EVO rack? Also, are these racks that tough that you can't do them yourself? Thanks for any help.

damon

Trust but verify:

"Electronic Variable Orifice" or EVO system. Ths is variable assist for the PS system.

Fairly certain that they mean the Solenoid. I posted a pic of one here long ago. It is a damn expensive part if you have to buy one new.

Hint: Look for post about cleaning the screen in the solenoid.

Luv Da Lex

i know your pain. my old ls400 was always running out of PS fluid so i always had to drive wihtout it. driving that boat without ps was a workout. that summer my arms got big due to the fact that i'll drive without ps cus i was too lazy to put fluid in. does it smoke during start up. i remember my car whoever did the ps system reverse a hose or something and the fluid got sucked into the intake system and it would blow white smoke on start up.